1. Field of the Invention
The present invention generally relates to a global positioning system (GPS) antenna, and in particular, to an apparatus for maintaining GPS antenna element at a predetermined angular orientation.
2. Description of the Related Art
In the field of GPS technology, GPS receivers are used to determine its geographic location by receiving microwave radio signals from a group of orbiting GPS satellites. The geographic location of the receiver may be computed by calculating its distance from each satellite by determining how long the signals took to travel from the satellite to the receiver. Typically, a flat GPS antenna element is utilized by GPS receivers to receive signals transmitted from the satellites. In order for the GPS receiver to accurately compute its geographic location, the GPS antenna element must be oriented in such a way as to receive an acceptable level of GPS signals from the satellites.
A variety of portable devices have been proposed for incorporating GPS receiver therein, and are becoming increasingly popular due to the availability of low cost GPS receivers and a wide variety of GPS applications. For example, a GPS receiver may be incorporated into a portable device (e.g., cellular phone, handheld GPS navigation system) to provide various functionality such as to determine its location, to provide navigation information or to remotely provide others with the information about the user's current location. At least in some of the portable devices having a GPS receiver incorporated therein, the GPS antenna is fixedly attached to the portable units.
Such prior art method of fixedly attaching the GPS antennas to the portable unit suffers from various disadvantages. For example, because the intensity level of the signals received by the GPS antenna depends on the angular orientation of the antenna element, the signal level received by the GPS antenna will vary as the orientation of the portable unit changes during operation thereof. As a result, a user of the conventional portable device must manually change the orientation of the device until the GPS antenna is able to receive an acceptable level of GPS signals.
In addition to applications in portable devices, GPS receivers are incorporated into vehicles for general navigational use. At least in some of the GPS receivers associated with vehicles, the GPS antenna is fixedly attached to a stationary part of the vehicles (e.g., windshield, backglass, roof panel). As previously mentioned, if the GPS antenna is fixedly attached to a stationary structure, the intensity level of GPS signals received by the GPS antenna will depend on the orientation of the vehicle. Consequently, as the orientation of the vehicle changes as the vehicle maneuvers up or down a hill, the signals received by the GPS antenna will vary and may fall below an acceptable signal level in certain situations.